The present invention relates generally to the field of manufacture of electronic devices. In particular, the present invention relates to the planarization of a substrate used in the manufacture of electronic devices, and more particularly to the filling of apertures.
In the manufacture of electronic devices, such as printed wiring boards or semiconductors, a number of layers of material, such as photoresists or antireflective coatings, are applied to a substrate. It certain instances, it is desired that the applied layer be conformal, whereas in other instances it is desired that the applied layer be planarizing. In particular, difficulties can arise in the patterning of upper layers in an integrated circuit structure where the lower layers have substantial topography. One difficulty in such patterning is the vertical excursion which can be substantial. For example, vertical variations as much as a micron or two are possible. Such vertical variation makes it difficult to focus the optical pattern, since the vertical excursions may take portions of the surface out of the available depth of field. In such situations, it is advantageous to place the photoresist layer all at the same height, or planarized, to potentially enhance available depth of focus.
One method of placing a photoresist at the same height over a surface is disclosed in U.S. Pat. No. 4,557,797 (Fuller et al.) which uses a multi-layer structure having a relatively thick bottom layer of poly(methyl methacrylate) (xe2x80x9cPMMAxe2x80x9d) to provide a planar surface, a thin middle layer of an antireflective coating and a thin top layer of a photoresist material. However, this system results in a thick polymer layer which must be removed. Such layers are typically removed by a variety of methods, such as chemical mechanical polishing (xe2x80x9cCMPxe2x80x9d), etching and wet chemical methods. Due to the added time and cost of such removal processes, it is desired that the polymer layers be as thin as possible to aid in their subsequent removal.
Certain antireflective coatings themselves may planarize the surface of a substrate sufficiently to allow effective use of a photoresist. For example, see Adams et al., Planarizing AR for DUV Lithography, Microlithography 1999: Advances in Resist Technology and Processing XVI, Proceedings of SPIE, vol. 3678, part 2, pp 849-856, 1999. However, such antireflective coatings are not disclosed to completely fill apertures, such as vias and trenches, and have relatively low etch resistance and moderate to low gap filling ability. Etch resistance is important in dual damascene processes where the bottoms of vias need to be protected during etching of the trenches. Current antireflective coatings are not sufficiently gap filling to completely fill the bottoms of small features, particularly sub-quarter-micron sized features, and may not be sufficiently resistant to such etch processes to protect the bottoms of vias during trench etching.
U.S. Pat. No. 5,976,703 (Nakata et al.) discloses a planarization layer for printed wiring board substrates. Such planarization layers use polysilphenylenesiloxane or copolymers of polysilphenylenesiloxane with an organosiloxane. These polymers are capable of planarizing features having geometries in the range of 10 to several hundred xcexcm. Such polymers are not disclosed for use in semiconductor manufacture and are limited in their ability to withstand subsequent processing steps, such as in dual damascene manufacturing processes.
There is thus a continuing need to provide planarized surfaces and aperture filling material having sufficient etch resistance to protect the bottoms of features during subsequent processing steps.
It has been surprisingly found that the present invention provides substantial local planarization of surfaces with less overcoating, has better gap filling capabilities and better etch resistance than known compositions. It has also been surprisingly found that the present invention provides protection of features, particularly the bottoms of small apertures during subsequent processing steps. The present invention is thus particularly useful in the manufacture of semiconductors using dual damascene processes.
In one aspect the present invention provides a composition comprising one or more cross-linkable polymers having a weight average molecular weight of less than or equal to about 8000 and a value of Mw/Mn of at least 1.5, one or more acid catalysts, one or more cross-linking agents and one or more solvents, wherein the cross-linkable polymers include as polymerized units at least one hydroxyl group containing monomer, and wherein the hydroxyl group is at least about 3%wt of the cross-linkable polymers.
In a second aspect, the present invention provides a substrate having apertures wherein the apertures contain a composition including the composition described above.
In a third aspect, the present invention provides a method of protecting the bottom of apertures in the manufacture of an electronic device including the steps of disposing on a surface of a substrate having apertures the composition described above; and heating the substrate at a temperature sufficient to at least partially cure the composition.
In a fourth aspect, the present invention provides a substrate having apertures wherein the apertures comprise a composition comprising one or more cross-linked polymers comprising as polymerized units one or more cross-linkable polymers having a weight average molecular weight of less than or equal to about 8000 and a value of Mw/Mn of at least 1.5 and one or more cross-linking agents, wherein the cross-linkable polymers comprise as polymerized units at least one hydroxyl group containing monomer, and wherein the hydroxyl group is at least about 3%wt of the cross-linkable polymers.
In a fifth aspect, the present invention provides a method of providing a substantially planarized surface including the steps of disposing on a surface of a substrate a composition comprising one or more cross-linkable polymers having a weight average molecular weight of less than or equal to about 8000 and a value of Mw/Mn of at least 1.5, one or more acid catalysts, one or more cross-linking agents and one or more solvents, wherein the cross-linkable polymers include as polymerized units at least one hydroxyl group containing monomer, and wherein the hydroxyl group is at least about 3%wt of the cross-linkable polymers; and at least partially curing the composition by heating the substrate at a temperature sufficient to at least partially cure the composition.
In a sixth aspect, the present invention provides a method for manufacturing an electronic device including the steps of: a) providing two or more first apertures in a substrate; b) at least partially filling the two or more first apertures with an aperture fill composition including one or more cross-linkable polymers having a weight average molecular weight of less than or equal to about 8000 and a value of Mw/Mn of at least 1.5, one or more acid catalysts, one or more cross-linking agents and one or more solvents, wherein the cross-linkable polymers comprise as polymerized units at least one hydroxyl group containing monomer, and wherein the hydroxyl group is at least about 3%wt of the cross-linkable polymers; c) heating the substrate at a temperature sufficient to at least partially cure the composition; d) plasma etching a feature connecting two or more at least partially filled first apertures; and e) removing the at least partially cured composition from the two or more first apertures.
In a seventh aspect, the present invention provides a method of protecting the bottom of apertures in the manufacture of an electronic device including the steps of disposing on a surface of a substrate having apertures in a layer an aperture fill composition including one or more cross-linkable polymers having a weight average molecular weight of less than or equal to about 8000 and a value of Mw/Mn of at least 1.5, one or more acid catalysts, one or more cross-linking agents and one or more solvents, wherein the cross-linkable polymers include as polymerized units at least one hydroxyl group containing monomer, wherein the hydroxyl group is at least about 3%wt of the cross-linkable polymers, wherein at least one of the cross-linkable polymer and the cross-linking agent include as polymerized units an aromatic monomer, and wherein at least one of the cross-linkable polymer and the cross-linking agent include as polymerized units an aliphatic monomer; and heating the substrate at a temperature sufficient to at least partially cure the composition; wherein the plasma etch rate of the aperture fill composition and the plasma etch rate of the aperture containing layer are substantially matched.
In an eighth aspect, the present invention provides a substrate having one or more apertures in a layer wherein the one or more apertures contain an aperture filling composition including cross-linked polymer, wherein the plasma etch rate of the cross-linked polymer and the plasma etch rate of the aperture containing layer are substantially matched.